Microscopic examination of the edge of the plaque showed a thin epidermis with the loss of rete ridges. A cornoid lamella was seen on the surface. The epidermis below the tier of parakeratosis showed an absence of the granular layer and mild nuclear atypia, features that are diagnostic of porokeratosis. Microscopic examination of the verrucous nodule revealed a hyperplastic epidermis, hyperkeratosis, parakeratosis, and red blood cells contained within the stratum corneum. The rete ridges were elongated and fused, and there were occasional vacuolated keratinocytes, suggestive of verrucous vulgaris.
Warty Nodules on an Annular Plaque in a Renal Transplant Recipient—Diagnosis. Arch Dermatol. 2004;140(1):121-126. doi:10.1001/archderm.140.1.121-h